1. Field of the Invention
This invention relates to a coordinate measuring instrument, wherein a measuring element is displaceable on two or more axes perpendicularly intersecting one another as in a two-dimensional and three-dimensional measuring instruments and a configuration or the like of a work to be measured can be measured from a displacement of this measuring element.
2. Description of the Prior Art
Two-dimensional and three-dimensional measuring instruments, wherein a measuring element displaceable in two-dimensional or three-dimensional directions is brought into contact with a surface of a work to be measured and a configuration or the like of the work is measured from the displacement of the measuring element, are utilized in every fields of industry because of their high measuring accuracy.
The three-dimensional measuring instrument is provided with a mechanism, by which the measuring element can be displaced in directions of X-, Y- and Z-axis perpendicularly intersecting one another.
As a mechanism for displacing the measuring element in directions of three axes, there has been provided one in which, for example, a plurality of supports are erected on the top surface of a bedplate, two rails extending in the direction of Y-axis are provided in parallel to each other on these supports, a beam extending in the direction of X-axis is stretched across these rails in a manner to be movable in the direction of Y-axis, a slider is mounted on the rail provided on this beam in a manner to be movable in the direction of X-axis, further, a spindle is provided on this slider in a manner to be slidable in the direction of Z-axis, and a measuring element is fixed to one end of this spindle. In other words, this mechanism as a whole has been constructed by a stacking system and the positional reference thereof has been sought from the bedplate or another basis.
In consequence, the conventional construction has presented such disadvantages that the configuration of legs should have borne the load as a structure of making the measuring element to move in the coordinate directions, whereby the construction should necessarily be large-sized, while the measurable scope is extremely limited. Furthermore, the supports should be vertical to the bedplate or the like and in parallel to opposite sides thereof, further, the height of the supports should be accurately finished and assembled, and the adjustments in these works should be made in .mu.m order, thus requiring excessive labor hours.
Furthermore, a main scale is provided on the side of the bedplate along the moving direction of the supports and an index scale opposed to the main scale is provided on the side of the supports, and the position of the supports are detected by the scales. However, if the main scale is directed upwardly, the main scale is subjected to damages and contaminations depending on the environment of use, thus possibly causing a trouble to detecting the position.
On the other hand, if the main scale is disposed transversely, damages and adhesion of contaminations may be relieved, however, a lock knob or the like for locking the supports should be mounted to the top surface thereof, with the result that, the lock knob or the like protrudes upwardly from the top surface of the bedplate, thus possibly causing a trouble to the carry-in and carry-out works for the work to be measured.
Further, the supports should be vertical to the bedplate or the like and in parallel to the opposite sides thereof, the supports should be accurately finished and assembled in their heights, subsequently, the structure to be supported by these supports should be assembled to be in parallel and vertical to the X-, Y- and Z-axes successively, and further, after the adjustments are made in this assembled structure, scales are fixed in a manner to be in parallel to the slider and the like with predetermined clearances, thus requiring extremely complicated steps and high skill level.
This leads to that the finishing accuracy of one of the parts renders a great influence to the total accuracy, if there occurs any disorder in the first stage, then correction or improvements cannot be effected, and finally, all of the adjustments and assemblings should be done over again. Furthermore, the skill level of an assembling worker exerts a great influence on the total accuracy.